# Tracking lineages of single cells in lines using a microfluidic device

Entry by Angelo Mao, AP 225, Fall 2010

Title: Tracking lineages of single cells in lines using a microfluidic device

Authors: Amy C. Rowat, James C. Bird, Jeremy J. Agresti, Oliver J. Rando, David A. Weitz

Journal: Proceedings of the National Academy of Sciences

Volume: 106(43)

Pages: 18149-18154

## Summary

Phenotypes vary down generations, but the time scale of variation in relation to cell division has not been elucidated because research platforms have been unable to isolate single cells to track their generations. The researchers created an in vitro microfluidics device that could trap single cells and observe their and their progeny's protein expression. The researchers demonstrated that the device could observe protein expression in real time, and applied this technique to three proteins that varied in expression across generations. Though the mechanisms are unclear, this research showed that phenotypic variation occurred to different degrees even in progeny of a single parent cell.

Soft Matter Keywords: microfluidics, epigenetics, in vitro

## Device Fabrication

To trap single cells, researchers designed channels (Fig 1A) with dimensions large enough for one cell, but constricted at the end so as not to let the cell escape. To prevent clogging of the channel, the researchers included bypass channels and calculated the expected flow rate through expected channels by modeling the system in terms analogous to electric circuits and by using the Hagen-Poiseuille relation.

$\frac{Q_{2}}{Q_{1}} = \frac{R_{1a} + R_{1b}}{R_{2}} = \frac{h_{2}^3 w_{2}}{l_{2}} (\frac{l_{1a}}{h_{1a}^{3} w_{1a}} + \frac{l_{1b}}{h_{1b}^{3} w_{1b}})$

Here, the ratio describes the volumetric flow rate ratio of the bypass channel to the trapping channel. The variables h, w, and l stand for height, width and length.

## Results and Conclusion

The researchers used yeast as model eukaryote cells to test their device. Since a constant nutrient source was necessary for cell viability, the researchers ensured by using fluorescent markers that, even in channels where cells were trapped, cell media was available.